DE69635587T2 - ULTRASONIC DEVICE FOR FIXING BONE PROPERTIES - Google Patents

Description

AREA OF INVENTION

The The present invention relates generally to a device for destructive Measurement of mechanical properties of materials as well as a Nondestructive device Measurement of mechanical properties of bone and bone quality.

BACKGROUND THE INVENTION

It It is known in the art that the speed of a sound wave in a material of the mechanical properties of the material depends. This phenomenon is z. As described by C.H. Hastings and S.W. Carter in an article entitled "Inspection, Processing and Manufacturing Control of Metal by Ultrasonic Methods, Symposium on Ultrasonic Testing, 52. Annual Meeting of the American Society for Materials Testing, 28. June 1949, p. 16-47.

The U.S. Patents 3,720,098, 3,228,232, 3,288,241, 3,372,163, 3,127,950, 3.512.400, 4.640.132, 4.597.292 and 4.752.917 describe the state the technique of non-destructive exam by ultrasound.

VS = αVT (3a)

wobei V_L, V_T und V_S die Geschwindigkeiten der longitudinalen, der transversalen bzw. der Raleigh-Oberflächenwelle sind und E, σ und rho das Young-Modul, das Poisson-Verhältnis von lateraler Kontraktion und longitudinaler Ausdehnung bzw. die Massendichte des Werkstoffs sind. Die Gleichung (3b) ist eine empirische Beziehung, die auf Seite 326 des Dokuments "Wave Motion in Elastic Solids" von Karl F. Graff definiert ist, das durch Clarendon Press, Oxford, England, 1975 veröffentlicht wurde.A sound wave striking an infinite semi-solid at an angle will typically propagate through and along the solid in the form of three waves, as longitudinal, transverse, and surface waves, each wave having a different velocity. As described by Hastings and Carter, the three waves have the following speeds:

V S = αV T (3a)

where V _L , V _T and V _{S are} the velocities of the longitudinal, transverse and Raleigh surface waves, respectively, and E, σ and rho are the Young's modulus, the Poisson ratio of lateral contraction and longitudinal expansion and the bulk density of the material, respectively are. Equation (3b) is an empirical relationship defined on page 326 of the document "Wave Motion in Elastic Solids" by Karl F. Graff, published by Clarendon Press, Oxford, England, in 1975.

In ultrasound measurement of the condition of bone, typically only the velocity of the longitudinal wave is used. In an article entitled "Osteoporotic Bone Fragility: Detection by Ultrasound Transmission Velocity", RP Heaney et al., JAMA, vol. 261, no. 20, 26 May 1989, pp. 2986-2990, the Young's modulus E of Bone empirically given as: E = K (rho) 2 (4a)

The velocity of the longitudinal acoustic wave in the bone is given as: VL = √ (E / rho) = √ (K * rho) (4b) where K is a constant containing several factors, such as the spatial orientation of the bone structures, inherent properties of the bone material, and fatigue damage. Therefore, the velocity of the longitudinal wave is a function of mass density and can be used as an indication of bone quality.

The following articles also explain the ultrasound measurement of the bone condition both in the living organism (in vivo) and in the prepared organism (in vitro):
"Measurement of the Velocity of Ultrasound in Human Cortical Bone In Vivo", MA Greenfield et al., Radiology, Vol. 138, March 1981, pp. 701-710; and
"Combined 2.25 MHz ultrasound velocity and bone mineral density measurements in the equine metacarpus and their in vivo applications", RN McCartney and LB Jeffcott, Medical and Biological Engineering and Computation, Vol. 25, 1987, Nov. 1877, p. 620 -626.

Around on the living organism ultrasonic measurements of the mechanical properties of the bone, must transmit an ultrasonic wave through the soft tissue surrounding the bone become. The thickness of the soft tissue unfortunately changes over the Length of the Bone. This change in thickness can affect the accuracy of the ultrasonic propagation time measurement. In the above mentioned Articles, the thickness of the soft tissue is either ignored or an attempt is made to neutralize the effects of soft tissue. In the articles that prepared in-vitro experiments (experiments on Organism), the soft tissue is removed from bone.

Russian Patents 1,420,383, 1,308,319, 1,175,435, 1,324,479, 1,159,556 and 1,172,534, and U.S. Patents 2,926,870, 4,361,154, 4,774,959, 4,421,119, 4,941,474 , 3,847,141, 4,913,157 and 4,930,511 describe various systems for measuring the strength of bones based on velocity V _L. These systems typically have an ultrasonic signal transmitter and at least one ultrasonic signal receiver.

In Russian patents 1.420.383, 1.308.319 and 1.175.435 trying to solve the problem of unknown thickness of soft tissue to solve, by taking values of the thickness of the soft tissue in the range of measurement or by assuming that the thickness change over the Distance between the two ultrasonic receivers is low.

in the Russian patent 1,342,279 will be two receivers and a single transmitter used and it becomes an average group speed calculated by the bone based on the distance between the two receivers.

in the Russian patent 1,159,556 defines zones of a bone and the condition of a bone is determined by the difference between the maximum and the minimum amplitude of the measured ultrasonic signal determined, with different zones different speeds have. It seems that this measurement is on a surgically removed Executed bones becomes.

in the Russian Patent 1,172,534 describes a system in which the ultrasonic signal of a healthy bone with that of a sick one Bone is compared and from the comparison a diagnosis of the scope the disease is derived in the diseased bone.

In U.S. Patents 4,926,870, 4,421,119, and 3,847,141 describe systems described in which a receiver and a transmitter on opposite Sides of a bone can be arranged. In U.S. Patent 4,926,870 will also comparing a resultant signal with a canonical waveform, to classify the state of health of the bone.

In U.S. Patents 4,913,157, 4,774,959 and 4,941,474 describe systems described in which an ultrasonic signal with a frequency spectrum is sent out.

in the U.S. Patent 4,930,511 describes a system that is standardized Lifeless homogeneous material with known acoustic properties is placed before it is placed around a bone.

In U.S. Patent 5,143,072, the disclosure of which is incorporated herein by reference, a method for overcoming the effects of unknown thickness of the intervening soft tissue is described. 1A , which illustrates the method of this patent, shows an ultrasonic transmitter 2 and two ultrasonic receivers 4 and 6 that are all colinear. The transmitter 2 sends an ultrasonic wave through soft tissue 22 to a bone eighteen , The first signal, the receiver 4 is received, runs through the fastest path. This path contains a first soft tissue path section 8th , a bone surface section 10 and a second soft tissue pathway section 14 , An angle 23 between the way 8th and the way 10 is determined by the relationship between the speed of sound in the bone eighteen and the speed of sound in soft tissue 22 certainly. The first signal from the receiver 6 is received, passes through the first soft tissue path section 8th , the bone surface section 10 , one too additional bone path section 12 and a third soft tissue pathway section 16 , The propagation times for the first received signal at the receivers 4 and 6 are measured. If the receiver 4 and 6 are aligned so that the way 14 and the way 16 have the same length, a subtraction of the two signal propagation times gives the propagation time in the bone section 12 , Because the bone section 12 the same length as the distance between the receiver 4 and the receiver 6 , the speed of sound in the bone section 12 be determined.

1B shows a method disclosed by the '072 patent, ensuring that the path 16 and the way 14 have the same length. The recipients 4 and 6 are also transmitters at the same time and they are used to calculate the wave propagation times along the paths 30 (and 32 ) between the recipients 4 (and 6 ) and the bone eighteen to eat. In an additional disclosed embodiment, the transmitter 2 and the recipients 4 and 6 attached to a tilting device that supports the soft tissue 22 when tilting squeezes, so that when the propagation times along the ways 30 and 32 are equal, the speed of sound of the bone is determined.

However, even this method has several serious disadvantages. First, the soft tissue velocity is not a constant, but it varies with the type of soft tissue. Because the propagation paths 30 and 32 not equal to the ways 14 and 16 are, the propagation times along the paths 14 and 16 be different and the calculated speed of sound of the bone is not correct, even if the propagation times along the paths 30 and 32 are the same. Second, the method described above requires a relatively long section of flat bone. As a result, only a small number of bones, such as the tibia, can be tested by this method. In addition, since high-frequency ultrasonic waves are very lossy, it is impractical to use them in this method. Third, the spatial resolution of this method is relatively small at about 2-5 cm.

SUMMARY THE INVENTION

It is an object of some aspects of the present invention, a method for determining the speed of sound of bones, that a high resolution owns, to create. Furthermore a small section of the bone can be measured so that almost all bones of the human body using a preferred embodiment of the present invention can be measured.

• (1) Senden eines ersten Ultraschallsignals längs eines Übertragungsweges von dem Sender durch das den Knochen umgebende Weichgewebe zu dem Knochen, längs der Oberfläche des Knochens und durch das Weichgewebe zurück zum Empfänger;
• (2) Messen der Ausbreitungszeit des schnellsten Signals zwischen dem Sender und dem Empfänger; und
• (3) Berechnen der Schallgeschwindigkeit des Knochens anhand des Abstands zwischen dem Sender und dem Empfänger, der Dicke des Weichgewebes und der Schallgeschwindigkeit in dem Weichgewebe.

In a preferred embodiment of the present invention, a transmitter and a receiver facing a bone are placed on the skin of a patient. The speed of sound in a bone is measured by:

• (1) transmitting a first ultrasonic signal along a transmission path from the transmitter through the soft tissue surrounding the bone to the bone, along the surface of the bone and through the soft tissue back to the receiver;
• (2) measuring the propagation time of the fastest signal between the transmitter and the receiver; and
• (3) Calculate the speed of sound of the bone based on the distance between the transmitter and the receiver, the thickness of the soft tissue and the speed of sound in the soft tissue.

One preferred method of calculating both the speed of sound reflected in the soft tissue as well as its thickness Waves. A transmitter and a transmitter / receiver are in a known Spaced apart on the skin, making the fastest Way from transmitter to transmitter / receiver does not pass through the bone. Instead, the fastest signal is from a point on the Bone to the transmitter / receiver reflected. It should be noted that the distance between the Transmitter and the transmitter / receiver can be very low. The propagation times of a signal generated by the transmitter to the transmitter / receiver is sent, and a signal sent by the transceiver and reflected back to the same transmitter / receiver through the bone will be measured.

• (a) eine erste Seite s₁, die die kürzeste Linie ist und den Sender und den Knochen verbindet;
• (b) eine zweite Seite s₂, die eine Linie ist, die am Sender/Empfänger beginnt und sich über die Hälfte des Abstands zwischen dem Sender und dem Sender/Empfänger erstreckt; und
• (c) eine Hypotenuse H, die die Linie zwischen dem Sender und dem Signalreflexionspunkt auf dem Knochen ist.

A right triangle is made up of the following three line segments:

• (a) a first side s ₁ , which is the shortest line and connects the transmitter and the bone;
• (b) a second side s ₂ , which is a line beginning at the transceiver and extending over half the distance between the transmitter and the transceiver; and
• (c) a hypotenuse H, which is the line between the transmitter and the signal reflection point on the bone.

Assuming that the thickness of the soft tissue under the transmitter is equal to the thickness below the sender Transmitter / receiver, s _{1 has} the same length as the distance between the transmitter / receiver and the bones. It can also be assumed that the average sound velocity of the soft tissue along all the measured paths is the same, because they are very close to each other. Therefore, the ratio between the first side and the hypotenuse is equal to the ratio between the measured propagation times. The length of the second side is easily calculated by the known formula: s ₁ ² + s ₂ ² = H ² . In fact, since the lengths s ₁ , s _2, and H are expressed as times, s _{2 is} actually the time that the signal would take to travel over half the known distance between the transmitter and the transceiver when the path in soft tissue. This determines the speed of sound of the soft tissue. The thickness of the soft tissue is now easily determined using the measured propagation time from the transmitter / receiver to the bone and back.

alternative Other methods for determining speed and thickness used. It is z. B. an X-ray image used to determine the thickness, and the speed becomes determined by measuring the time it takes a signal to from a sender / receiver to the bone and back along the Spread out.

The Thickness is preferably measured at the point where the signal from the transmitter to the receiver enters the bones. additionally or alternatively, the thickness of the soft tissue is measured at the point where the signal from the transmitter to the transmitter / receiver reflects off the bone becomes.

The Ways of the signal from the transmitter to the transmitter / receiver preferably overlap the Path of the signal from the transmitter to the receiver.

It It should be recognized that the preferred embodiments instead of depicting human or animal meat for analyzing wood, plastic, metal and composite materials, the with an outer one. coating made of a different material are, can be used.

It It should be recognized that the procedures described above for Determining speed and thickness of soft tissue are also useful in improving the accuracy of procedures, the state of the art Technique are to determine the speed of sound of bones.

A typical resolution, using the method described above for determining the Speed of sound of bones is less than 1 centimeter, typically less than 0.5 centimeters, and preferably smaller than 3 millimeters.

The mentioned above Sender and receiver are preferably mounted in a sensor having a long axis and has a short axis. The sensor is typically along its tilted long axis while carried out several measurements become. Preferred measurements of bone velocity are performed when the thicknesses of the soft tissue sections under the transmitter or under the receiver are equal, even if the average speed of sound is not the same.

Additionally or Alternatively, the sensor is longitudinal tilted his short axis while carried out several measurements become. Preferably, the dependence of the specific speed of sound of the bone determined by the tilt angle. Typically, the maximum certain speed than the representative speed of sound used.

According to one preferred embodiment The present invention also provides a method by an inserted Medium the thickness of a solid determining, the method comprising: transmitting a broadband ultrasonic wave along a Away from a first place through the medium and along the surface of the solid, Receive the wave at a second location and analyze the received Wave to the difference between the propagation time of the high-frequency Component of the wave and the propagation time of the low-frequency Determine component of the wave.

It Apparatuses and methods are provided in accordance with claims 1-52.

SUMMARY THE DRAWING

The Invention becomes more complete understood from the following detailed description of their preferred Embodiments, which takes place in conjunction with the drawing, in which:

1A shows a method for measuring the speed of sound of bones of the prior art;

1B an improvement of the prior art on the in 1 showing methods comprising additional measurements;

2 a method for measuring the speed of sound of bones according to a preferred embodiment of the present invention;

3 a method of determining the speed of sound of soft tissue according to a second preferred embodiment of the present invention;

4A shows a preferred method for measuring the speed of sound of bones, in which aspects of the method of the 2 and 3 combined;

4B A further preferred embodiment of the invention, in which aspects of the method of the 2 and 3 combined;

4C the procedure of 4A which is used in cases of equal and uneven thicknesses of the underlying tissue;

4D a simplified schematic partial representation of a portion of the method of 3 is;

4E a simplified schematic partial representation of a portion of the method of 2 is;

the 5A and 5B show a two-step method of measuring the speed of sound of bones according to another preferred embodiment of the present invention;

the 6A and 6B show a two-step method of measuring the speed of sound of bones according to yet another preferred embodiment of the present invention;

7A another method for measuring the speed of sound of bone according to another preferred embodiment of the present invention;

7B an idealized version of 7A shows;

the 8A and 8B preferred alternative versions of the in the 7A and 7B show the method shown;

9 is a schematic partial view of a cut human bone;

10 Fig. 11 is a graph showing the relationship between the thickness of an object and the velocity of an ultrasonic wave along its surface;

11 Fig. 12 is a schematic illustration of an alternative embodiment of the present invention utilizing an array of piezoelectric transducers;

12 a schematic representation of the arrangement of 11 which illustrates the connections of the transducers to control and signal processing elements;

the 13A and 13B show a method for analyzing soft tissue according to a preferred embodiment of the present invention; and

14 a method for simultaneous bone velocity determination and bone imaging according to a preferred embodiment of the present invention.

PRECISE DESCRIPTION THE PREFERRED EMBODIMENTS

The method for determining the speed of sound of bones according to a preferred embodiment of the present invention includes determining the velocity in the soft tissue. 2 shows a bone eighteen that of soft tissue 22 is surrounded. To determine the speed of sound of the bone, sends a transmitter 40 a signal to a receiver 44 and a propagation time T _total is measured. There are obviously many ways that the signal from the transmitter 40 to the recipient 44 can take, some of which from the bone eighteen be reflected and some along the surface of the bone eighteen run.

If a distance D ₄₀₄₄ between transmitter 40 and receiver 44 long enough, includes the fastest way, as in 2 shown is three segments. A first soft tissue segment 60 , a bone surface segment 64 and a second soft tissue segment 62 , The angle B _r between the segment 60 and a perpendicular to the segment 64 (Bone eighteen ) is the Brewster angle, which is defined as: B r = arcsin (v 22 / V eighteen ) (5) where V _{22 is} the velocity of the longitudinal wave in the soft tissue 22 and V is _18, the speed of a longitudinal surface acoustic wave in the bone eighteen is. If D _{4044 is} so short that no Brewster angle can be formed, the fastest way is the path of simple reflection from the bone eighteen ,

The speed of sound in the bone eighteen is calculated by dividing a length D _{64 of} the bone segment 64 by a time T ₆₄ , which is the signal for propagation across the bone segment 64 needed. However, neither D ₆₄ nor T _{64 is} known. In some prior art methods, V _{22 becomes} a distance H ₄₀ between the transmitter 40 and the bone eighteen and a distance H ₄₄ between the receiver 44 and the bone eighteen estimated. This results in a distance D ₆₀ , the length of the segment 60 is a distance D ₆₂ , which is the length of the segment 62 and their propagation times T ₆₀ and T _{62 are} :

D ₆₄ and T ₆₄ result from: D 64 = D 4044 - (H 40 tg (B r ) + H 44 tg (B r )) (10) T 64 - T total - (T. 60 + T 62 ) (11)

Thus V _{18 is} :

A solution of the simultaneous equations (5) - (12) yields V ₁₈ .

However, an estimate of H ₄₀ , H ₄₄ and V ₂₂ is not very accurate, especially since V ₂₂ is a function of distance from the bone eighteen changes. The tissues close to the bone eighteen are typically muscles and have an average speed that is 10% greater than that of fat, which is typically located closer to the skin.

• (a) Schätzen des Brewster-Winkels; und
• (b) Anordnen des Sender/Empfängers 42 an einem Ort, an dem ein Reflexionswinkel R_f, der der Winkel zwischen dem Segment 46 und einer Senkrechten zum Knochen 18 ist, kleiner als der Brewster-Winkel ist. Es ist in der Technik bekannt, dass dort, wo der Einfallswinkel kleiner als der Brewster-Winkel oder gleich diesem ist, der schnellste Weg nicht durch den Knochen 18 verläuft, sondern lediglich von ihm reflektiert wird.

3 FIG. 10 shows a method for determining H ₄₀ , H ₄₄ and V ₂₂ according to a preferred embodiment tion form of the invention. A transmitter / receiver 42 is colinear between the transmitter 40 and the receiver 44 arranged so that the fastest way between stations 40 and receiver 44 no path segment in the bone eighteen having. As in 3 is the fastest way between stations 40 and transceiver 42 a first soft tissue segment 46 and a second soft tissue segment 48 , A method for arranging the transceiver 42 in such a place includes:

• (a) estimating the Brewster angle; and
• (b) Arrange the transceiver 42 in a place where a reflection angle R _f , which is the angle between the segment 46 and a perpendicular to the bone eighteen is less than the Brewster angle. It is known in the art that where the angle of incidence is less than or equal to the Brewster angle, the fastest path is not through the bone eighteen runs, but is only reflected by him.

First, V _{22 is} measured. A signal is sent from the transmitter 40 to the transmitter / receiver 42 and its propagation time T ₄₆ + T ₄₈ is measured. A second signal is from the transmitter / receiver 42 to the bone eighteen sent and along a path segment 50 reflected back. An isosceles triangle is formed from:

• (a) the line that the transmitter 40 and the transceiver 42 connects and has a length D ₄₀₄₂ ;
• (b) the segment 46 having a length D ₄₆ ; and
• (c) the segment 48 which has a length D ₄₈ .

Assuming that the thickness of the fabric 22 in the small area between transmitters 40 and transceiver 42 constant, owns the segment 50 a length D ₅₀ equal to the height of the isosceles triangle.

It is assumed that the average value of V ₂₂ along the segments 46 . 48 and 50 is the same, D ₄₆ , D ₄₈ and D ₅₀ become: D 46 = V 22 * T 46 (13) D 48 = V 22 * T 48 (14) D 50 = V 22 * T 50 / 2 (15)

By Apply a known relationship between the pages and the height of a page isosceles triangle results:

By solving equation 16 using equations 14 and 15 and using equality between T ₄₈ and T _46, we obtain:

However, since T ₅₀ , T ₄₈ and D _{4042 are} known, it follows:

It should be noted that the value V ₂₂ calculated above is an average value along the actual path of the signal, ie it contains the weighted values of both the velocity in adipose tissue and the velocity in muscle tissue.

It is assumed that H _{44 is} equal to H ₄₀ (which is equal to D ₅₀ ). Thereby: H 44 = H 40 = V 22 * T 50 (19)

If greater precision is required or to reduce interference, V ₂₂ is a second time calculated using the signal propagation time between the transmitter / receiver 42 and the receiver 44 in place of the signal propagation time between the transmitter 40 and the transceiver 42 , The distance between the transmitter / receiver 42 and the receiver 44 is of course also such that the reflection angle is less than or equal to the Brewster angle. V ₂₂ is calculated using the average of the first and second calculations.

Alternatively to the method described above for measuring V ₂₂ , H ₄₀ and H ₄₄ , other methods may be used. H ₄₀ and H ₄₄ can, for. B. be measured on an X-ray or other medical presentation. V ₂₂ is then based on the signal propagation time of the reflection from the bone eighteen measured.

The 4A and 4B show a measuring sensor of the speed of sound of the bone according to another preferred embodiment of the present invention. A transmitter 70 , a transmitter / receiver 72 and a receiver 74 become colinear on soft tissue 22 arranged that the bone eighteen surrounds. As described above, the distance is between the transmitter 70 and the transceiver 72 such that a signal coming from the transmitter 70 to the transmitter / receiver 72 moved, not through the bone eighteen runs. Preferably also the fastest way is from the transmitter / receiver 72 to the recipient 74 not through the bone eighteen ,

V ₂₂ and the thickness of the soft tissue 22 in the area close to the transmitter / receiver 72 are then determined in the manner described above. The speed of sound in the bone eighteen is then used to transmit a signal from the transmitter using the method described above 70 to the recipient 74 certainly. Preferably, the distance between the transmitter 70 and the transceiver 72 such that a signal traveling between them is reflected at an angle R _f1 approximately equal to the Brewster angle, as in FIG 4B is shown. This measures _V22 along the same path as the signal path for measuring bone velocity. Since the Brewster angle in human flesh is between 20 ° and 28 °, an angle of 24 ° is a good estimate, with the result that the paths almost overlap.

The transmitter / receiver 72 is preferably in the middle between transmitters 70 and receiver 74 , If the line, the transmitter 70 and the receiver 74 does not connect exactly parallel to the bone eighteen Because of this, the fact that the thickness of the soft tissue is measured between them serves to give a close approximation to the average speeds.

The minimum required wave propagation distance in the bone using this method is about 2-3 millimeters. The distance between the transmitter 70 and the receiver 74 depends on the thickness of the soft tissue. Using this method, a high resolution imaging of relatively uneven bones is possible. Such bones contain z. As vertebral bone, the small bones in the wrist and bone sections close to joints. It is also possible to measure the bone velocity both in the longitudinal direction and in the transverse direction, since the length of the measured bone segment can be very small.

A preferred operating frequency is between 250 and 1500 kHz. It It should be noted that higher Frequencies as the frequencies used in the prior art despite the stronger one Damping of High-frequency sound waves in the bone can be used there the stretches that move the signals in the bone, short are. higher Frequencies generally give more accurate results than lower ones Frequencies. In some preferred embodiments of the present invention Invention, the operating frequency is preferably above 2 MHz, where a value is over 5 MHz stronger is preferred and in some preferred embodiments of the present Invention, the preferred operating frequency is greater than 10 MHz. The wave is preferably pulsed for a duration between 2 and 250 milliseconds.

The used waveform is preferably a pulse-shaped wave with a single frequency, as the only aspect of the analyzed Wave is the time of the first reception of a signal. Alternatively other more complex waveforms are used and the received signals will be analyzed.

The transmitter 70 and the transceiver 72 are preferably aligned so that they emit their signals primarily at an angle that is the estimated Brewster angle, as is known in the art. Besides, the receiver 74 and the transceiver 72 preferably, such that they have a high reception gain at the estimated Brewster angle.

If the transmitter 70 and the transceiver 72 aligned at the Brewster angle, the sensor surface is typically concave and not flat. This concave space is preferably filled with a uniform material having a known speed of sound. In a preferred off According to the invention, the speed of sound of the filling material is close to that of the soft tissue, so that the influence of the filling material on the calculations described here can be ignored. Alternatively, the influence of the layer of filler on sonic velocity calculations may be estimated and taken into account either during calibration or in a multi-layered structure as the upper layer influence as described above.

It should be recognized that the two steps of the above Process in any order or run concurrently can. For each Signal preferably different frequencies are used. It should be recognized that the ultrasonic transmitter used and the ultrasonic receiver used is typically a very size Own bandwidth. As a result, several wavelengths are emitted and every receiver processes its incoming signals to filter out specific frequencies and capture. Alternatively or additionally, the pulses are timed controlled so that at a single receiver never has two pulses in common Arrive.

The transmitter 70 , the transmitter / receiver 72 and the receiver 74 are preferably by a control unit 100 controlled. The triggering of the signals described above, the measurement of times, the signal processing and the speed calculation are therefore performed by the control unit 100 executed.

A three-element sensor, such as that with reference to FIGS 4A and 4B The sensor described above is preferably designed to be shorter than 100 millimeters, with a shorter value than 50 millimeters more preferred, and in some preferred embodiments the sensor is shorter than 3 millimeters. In a particular preferred embodiment, the sensor has a length of 32 millimeters. The maximum distance allowed between such a sensor and a bone is about 2 centimeters. Because of the very high accuracy requirements of such a sensor, it is preferably constructed of a material that does not substantially expand or contract in the temperature range of 15 to 40 ° C. Such materials typically include a mixture of a material that expands when heated from 15 to 40 ° C and a material that contracts when heated from 15 to 40 ° C.

It should be recognized that the distance between the ultrasonic elements for one certain expected depth of soft tissue can be optimized. Because of this, a typical operating system includes multiple sensors, each for a different range of depth are suitable. alternative becomes a single sensor of the lattice type described below is used.

The sensor is typically not designed to have an exact spacing between the ultrasonic elements. The sensor is instead constructed with an accuracy of about 0.1 millimeter and the exact distances between the elements are measured using an auxiliary body. The measurement results, which have a typical accuracy of over 2 μm, are stored in the control unit 100 for a speed determination, which will be described later in more detail. Such an auxiliary body comprises a plastic cylinder having an embedded in the plastic cylindrical metal core with steps which are formed along its axis. Each step corresponds to a known depth of plastic overlying the metal core.

The speed of sound of bones is typically different in different sections of the bone. Therefore, in order to conveniently compare two results of the speed of sound of bones from two different measurements, the measurements must be made on the same portion of the bone. The positional accuracy along the longitudinal axis of the bone should be in the order of 5 millimeters in detail for long bones, such as the tibia. This accuracy can be easily achieved using normal positioning methods, such as marking the location with a permanent marker point. However, the transverse positioning method must be on the order of 100 microns. Since this accuracy is difficult to achieve, the sensor is preferably mounted on a tilting device, so that the transmitter 70 , the transmitter / receiver 72 and the receiver 74 are along an axis of the tilting device, which are parallel to the longitudinal axis of the bone eighteen runs. When the sound velocity of the bone is measured, the tilting means is tilted in a transverse direction and a plurality of sound velocities of the bone are measured. The maximum or minimum determined value is used as the reference value for comparison with bone velocity measurements during other measurements. In addition or in addition, the speed of sound of the bone eighteen from different sides of the bone eighteen measured as the cortex of the bone eighteen typically several has different sections, each of which has a different hardness and speed of sound.

It it should be recognized that in some bones, such as the vertebral bone, Measuring the softer sections is easier than measuring the harder one Sections and thus the search for the minimum speed. The minimum certain speed is typically in the softest section. A minimum certain speed that for a later Is found in the softest section, therefore, the speed measurement becomes at the same transverse location (same section) repeated.

Additionally and additionally, the acquired velocity measurements are used to obtain a transverse velocity profile of the bone eighteen which is useful for analysis of bone structure.

4C shows the above with reference to 4A described embodiment in a manner that facilitates the following mathematical explanation. The purpose of this discussion is to more accurately analyze the mathematics of sound velocity determination. 4C shows two ways, one way in which the line containing the ultrasound elements 70 . 72 and 74 connects, parallel to the bone eighteen runs, and a second way in which the line containing the ultrasound elements 70 . 72 and 74 connects, not parallel to the bone eighteen runs. In each of these cases, the mathematical derivation of the speed of sound of the bone is different.

The 4D and 4E show the times actually measured in the method described above. The following equations associate these times 4C :

In addition, γ is the Brewster angle. In the following equations, "a" is the distance between points A and B (AB), b = BC, and c = CD. In addition, the letter A, if it does not refer to the point A, the sum of a + b + c, ie the shortest distance between the transmitter 70 and the receiver 74 ,

In a first, simplest case, which rarely occurs in practical situations, the line is the ultrasound elements 70 . 72 and 74 connects, parallel to the bone eighteen , That's why: H 1 = h 2 = h 3 = h 4 (24) sinα = 0 (25) τ 1 = τ 3 (26)

wobei die Schallgeschwindigkeit des Knochens V₁₈ oder V_b durch die folgende Gleichung bestimmt wird:The speed of sound of soft tissue V ₂₂ or V _t is determined as:

wherein the speed of sound of the bone V ₁₈ or V _{b is} determined by the following equation:

The solution results:

It should be noted that not only h ₁ = h ₂ = h ₃ = h ₄ applies to the determination of the speed of sound of the bone using the equations described above, but also τ ₁ = τ ₃ . As a result of soft tissue velocity changes resulting from soft tissue nonuniformities, this is rarely the case with in vivo measurements. However, one of the above two conditions can usually be met. In a preferred embodiment of the invention, the sensor is embedded in a tilting device. Such a tilting device is described in the above-mentioned U.S. Patent 5,143,072. The tilting device is along an axis that the transmitter 70 with the transmitter / receiver 72 and the receiver 74 connects, tips and several measurements of speed of a soft tissue and thickness of a soft tissue are carried out. Bone velocity measurements are then performed if either h ₁ = h ₂ = h ₃ = h ₄ or if τ ₁ = τ ₃ .

A special case is the measurement of the speed of sound of the thighbone. The surface geometry of the femur is essentially not planar in its sections. In addition, the thickness of the soft tissue above the femur is large and on the order of 6 cm. The measurements of the speed of sound of the bone are preferably carried out when the transmitter 70 and the receiver 74 are equidistant from the femur to minimize erroneous reflections.

If the connecting line of the ultrasonic elements 70 . 72 and 74 not parallel to the bone eighteen Usually, the following more complex equations must be solved to determine the speed of sound of the bone. The following equations assume that the configuration is similar to that in 4C configuration shown is (non-parallel configuration). If the configuration is a mirror image to that in 4C In the configuration shown, h ₂ should be measured at point C and the equations should be modified accordingly.

The velocity of sound of soft tissue V ₂₂ or V _t is determined using the following equations:

p2 = –2τ0Acosα (33)

p4 = 2τ0AVt 2cosα (35) p5 = – Vt 2 × [A2cos2α + (Vtτ2 + (b + c – a) × sinα)2] (36) The speed of sound of the bone is determined using an equation similar to equation (28): p 1 V B 4 + p 2 V B 3 + p 3 V B 2 + p 4 V B + p 5 = 0 (31) in which:

p 2 = -2τ 0 Acos (33)

p 4 = 2τ 0 AV t 2 cos (35) p 5 = - V t 2 × [A 2 cos 2 α + (V t τ 2 + (b + c - a) × sinα) 2 ] (36)

The exact length of the different path segments in the bone eighteen and in soft tissue 22 can be done using the geometric relationships that exist in 4C and the speed of soft tissue and bone as determined above. The path of the wave from the transmitter 70 to the recipient 74 in detail:

The 5A and 5B show an additional embodiment of the present invention. The speed of sound of the bone is measured using the method described above for measuring the propagation time of a signal transmitted by a transmitter 80 is sent out until it is first received by a recipient 86 is received, measured. However, this embodiment differs from the embodiment of FIG 4A and 4B to the effect that instead of the individual transceiver 72 a pair of transceivers 82 and 84 is used. First, the thickness of the fabric 22 and the speed of sound in the tissue 22 Measured in more than one place. As a result, areas of the body which have uneven surfaces or variable speeds of sound of the soft tissue are recognized. The operator is preferably notified and takes appropriate action, such as changing the measuring point. Alternatively, the speed of sound calculations are corrected because of these differences.

Second, the transmitter / receiver 82 independent of the transmitter / receiver 84 be arranged. In the embodiments of the 4A and 4B For example, a preferred situation has been described in which the path of the signals used to determine the speed of sound of the soft tissue coincides with the path used to determine the speed of sound of the bone. In the present embodiment, the transmitter / receiver 82 relative to the transmitter 80 be positioned so that this preferred situation occurs (in terms of 5B in the method described below). The transmitter / receiver 84 becomes similarly relative to the receiver 86 positioned. It should be noted that the distance between the transmitter 80 and the receiver 86 the measurement is not significantly adversely affected.

The 5A and 5B describe a two-step process in which some measurements are made in the first step and some measurements are made in the second step. However, the order of these steps does not matter and the two steps are preferably performed under Ver use of different frequencies or waveforms simultaneously. If a two-step method is used, the determination of the speed of sound of the bone is preferably performed in both steps.

However, performing only one of these two steps is sufficient for determining the speed of sound of the bone. The decision as to which step is performed is preferably based on the configuration of transmitter / receiver 82 , Transmitter-receiver 84 , Transmitter 80 , Receiver 96 and bones eighteen which influences the relative locations of soft tissue velocity measurement and bone velocity measurement.

• (a) die Dicke des Gewebes 22 unter dem Sender/Empfänger 82;
• (b) die Dicke des Gewebes 22 unter dem Sender/Empfänger 84; und
• (c) die Ausbreitungszeit eines Signals vom Sender/Empfänger 82 zum Sender/Empfänger 84.

In the step in 5A is described, the speed of sound of the bone is measured by the propagation time of a signal between the transmitter 80 and the receiver 86 is measured. In addition, the following measurements useful for soft tissue velocity determination are performed:

• (a) the thickness of the fabric 22 under the transmitter / receiver 82 ;
• (b) the thickness of the fabric 22 under the transmitter / receiver 84 ; and
• (c) the propagation time of a signal from the transceiver 82 to the transmitter / receiver 84 ,

These measurements are sufficient to determine the speed of sound of the soft tissue and to determine changes in the thickness of the tissue 22 , It should be noted that if the transmitter / receiver 82 and the transceiver 84 are sufficiently spaced so that a signal from the transmitter / receiver 82 to the transmitter / receiver 84 through the bone eighteen runs, the measurement (c) is not performed. The measurements (c) and (d) made in the step of 5B but compensate for the non-execution of the measurement (c).

• (a) die Dicke des Gewebes 22 unter dem Sender/Empfänger 82;
• (b) die Dicke des Gewebes 22 unter dem Sender/Empfänger 84;
• (c) die Ausbreitungszeit eines Signals vom Sender 80 zum Sender/Empfänger 82; und
• (d) die Ausbreitungszeit eines Signals vom Sender/Empfänger 84 zum Empfänger 86.

In the step in 5B is shown, the speed of sound of the bone is measured by the propagation time of a signal between the transmitter 80 and the receiver 86 is measured. In addition, the following measurements useful for soft tissue velocity determination are performed:

• (a) the thickness of the fabric 22 under the transmitter / receiver 82 ;
• (b) the thickness of the fabric 22 under the transmitter / receiver 84 ;
• (c) the propagation time of a signal from the transmitter 80 to the transmitter / receiver 82 ; and
• (d) the propagation time of a signal from the transceiver 84 to the recipient 86 ,

These measurements are sufficient to determine the speed of sound of the soft tissue and to determine changes in the thickness of the tissue 22 , In turn, the fastest way for a signal from the transmitter 80 to the transmitter / receiver 82 or from the transmitter / receiver 84 to the recipient 86 through the bone eighteen runs, the measurements (c) and / or (d) are not carried out. The measurement (c) made in the step of 5A is executed, but replaces these missing measurements.

It should be noted that the measurements made in the in 5B 5, which determine the speed of sound of the soft tissue in the local area surrounding the area in which a signal travels, which is used for the determination of the speed of sound in the bone. Thus, this embodiment is then suitable for the determination of the speed of sound in bone, if it is known from the surface be that it is uneven or if it is known that the speed of sound of the soft tissue changes. In addition, the determination of the speed of sound of bones is over curved body parts, such as along the transverse axis of bones eighteen , owing to the short way segment, that along a bone eighteen is required, possible.

The small dimensions of the minimum required bone pathway segment allows a sample with a high spatial resolution using the embodiments of the present invention. To z. B. the speed of sound in Measuring a section of the cortex of a tooth may involve a 10 MHz ultrasonic pulse be used. Due to the high frequency of the ultrasound, the Sensor dimensions of the order of magnitude of 3 mm, with the resolution is less than 1 mm.

The 6A and 6B show a further preferred embodiment using three transceivers, a transmitter and a receiver. As before, the speed of sound of the bone is determined by the propagation time of one of the transmitter 90 emitted signal to a receiver 98 is measured. A two-step process for determining the speed of sound of soft tissue is preferred.

• (a) Übertragungszeit vom Sender 90 zu einem Sender/Empfänger 92;
• (b) Übertragungszeit vom Sender/Empfänger 92 zu einem Sender/Empfänger 96;
• (c) Übertragungszeit vom Sender/Empfänger 96 zum Empfänger 98;
• (d) Dicke des unter einem Sender/Empfänger 94 liegenden Gewebes 22; und
• (e) Übertragungszeit vom Sender 90 zum Empfänger 98.

6A shows a first step where the following measurements are taken:

• (a) Transmission time from the transmitter 90 to a transmitter / receiver 92 ;
• (b) Transmission time from transmitter / receiver 92 to a transmitter / receiver 96 ;
• (c) Transmission time from transmitter / receiver 96 to the recipient 98 ;
• (d) thickness of under a transmitter / receiver 94 lying tissue 22 ; and
• (e) transmission time from the transmitter 90 to the recipient 98 ,

• (a) Übertragungszeit vom Sender/Empfänger 92 zu Sender/Empfänger 96;
• (b) Dicke des unter einem Sender/Empfänger 92 liegenden Gewebes 22;
• (c) Dicke des unter einem Sender/Empfänger 94 liegenden Gewebes 22;
• (d) Dicke des unter einem Sender/Empfänger 96 liegenden Gewebes 22; und
• (e) Übertragungszeit vom Sender 90 zum Empfänger 98.

6B shows a second step in which the following measurements are carried out:

• (a) Transmission time from transmitter / receiver 92 to transmitter / receiver 96 ;
• (b) thickness of under a transmitter / receiver 92 lying tissue 22 ;
• (c) thickness of under a transmitter / receiver 94 lying tissue 22 ;
• (d) thickness of under a transmitter / receiver 96 lying tissue 22 ; and
• (e) transmission time from the transmitter 90 to the recipient 98 ,

This will change the thickness of the fabric 22 Measured in three places, allowing changes in the thickness of the fabric 22 easier to include in the calculation.

The transmitter / receiver 92 and 96 are preferably arranged to match the thickness of the fabric 22 at the exact point at which it is estimated that the signal for determining the speed of sound of the bone enters and leaves the bone. The transmitter / receiver 94 is preferably arranged to match the thickness of the fabric 22 at the estimated point of reflections for signals from the transceiver 92 to the transmitter / receiver 96 measures. This is a more accurate estimate of the signal path length in the tissue 22 possible.

• (a) die Schallgeschwindigkeit des Weichgewebes wird separat für jeden Bereich bestimmt_; in dem sich das Signal durch das Gewebe 22 fortbewegt;
• (b) die Dicke des Gewebes 22 wird an dem Punkt gemessen, an dem das Signal in den Knochen 18 eintritt; und
• (c) der Weg des Signals fällt mit dem Weg zusammen, der für Signale zum Messen der Schallgeschwindigkeit des Weichgewebes verwendet wird.

The 7A and 7B show a further preferred embodiment of the present invention. As before, the sound velocity of the bone is measured by measuring the propagation time of a signal from a transmitter 110 to a receiver 120 certainly. However, there will be a number of four transceivers 112 . 114 . 116 and 118 used to measure the speed of sound of soft tissue. This embodiment includes several features that have been described in previous embodiments, and in particular in 7B shown are:

• (a) the speed of sound of the soft tissue is determined separately for each area _; in which the signal passes through the tissue 22 traveling;
• (b) the thickness of the fabric 22 is measured at the point where the signal enters the bone eighteen entry; and
• (c) the path of the signal coincides with the path used for signals to measure the speed of sound of the soft tissue.

As can be appreciated, the transceivers are preferably arranged in the manner disclosed in U.S. Pat 7B is shown, and not as in 7A is shown in order to achieve all the features mentioned above.

• (a) Messen der Ausbreitungszeit für ein Signal vom Sender 110 zum Sender/Empfänger 114 (wobei der Sender/Empfänger 114 lediglich ein Empfänger zu sein braucht);
• (b) Messen der Dicke des unter dem Sender/Empfänger 112 liegenden Gewebes 22; und
• (c) Berechnen der Dicke des Gewebes 22 und seiner Schallgeschwindigkeit in dem Bereich nahe am Sender 110 unter Verwendung von (a) und (b).

Preferably, two independent measuring operations are carried out. A first operation in the area close to the transmitter 110 is executed includes:

• (a) measuring the propagation time for a signal from the transmitter 110 to the transmitter / receiver 114 (where the transmitter / receiver 114 just to be a recipient);
• (b) measuring the thickness of under the transmitter / receiver 112 lying tissue 22 ; and
• (c) calculating the thickness of the fabric 22 and its speed of sound in the area near the transmitter 110 using (a) and (b).

• (a) Messen der Ausbreitungszeit für ein Signal vom Sender/Empfänger 116 zum Empfänger 120 (wobei der Sender/Empfänger 116 lediglich ein Sender zu sein braucht);
• (b) Messen der Dicke des unter dem Sender/Empfänger 118 liegenden Gewebes 22; und
• (c) Berechnen der Dicke des Gewebes 22 und seiner Schallgeschwindigkeit in dem Bereich nahe am Empfänger 120 unter Verwendung von (a) und (b).

The second process is very similar and will be close to the receiver 120 run:

• (a) measuring the propagation time for a signal from the transceiver 116 to the recipient 120 (where the transmitter / receiver 116 only one transmitter needs to be);
• (b) measuring the thickness of under the transmitter / receiver 118 lying tissue 22 ; and
• (c) calculating the thickness of the fabric 22 and its speed of sound in the area near the receiver 120 using (a) and (b).

In the embodiments included in the 4A - 7B are shown, all ultrasonic elements are preferably collinear. However, the correct sound velocities can be determined if the ultrasound elements are not collinear, but the distances between the ultrasound elements are known.

In the embodiments described above, a transceiver transmits and receives, such as about the transmitter / receiver 82 ( 5A ), an ultrasonic wave. The inventor has found that the reception quality of an ultrasonic transceiver is deteriorated for a short time after transmitting an ultrasonic wave. The measured received signal is the sum of the actually received signal and a transmission signal remainder. This degradation can be prevented by separating the transceivers into a pair of transmitter and receiver, respectively.

The 8A and 8B show such a separation, which is carried out on the embodiments, which in the 7A and 7B are shown. In 8A corresponds to a transmitter 130 the transmitter 110 (in 7A ), a transmitter 132 and a receiver 134 correspond to the transmitter / receiver 112 , a receiver 136 corresponds to the recipient 114 , a transmitter 138 corresponds to the transmitter 116 , a transmitter 140 and a receiver 142 correspond to the transmitter / receiver 118 and a receiver 144 corresponds to the recipient 120 , The method of operation is as described above with reference to FIG 7A described method with the exception of the thicknesses under the transmitter / receiver 112 and 118 which are measured not with a transceiver but using a transmitter and a receiver. Measuring the thickness of the soft tissue using a transmitter and a receiver is as accurate as using a single transceiver because the distance between the transmitter and the receiver (ie the distance between the transmitter 132 and the receiver 134 ) is much shorter than the thickness of the soft tissue 22 , Besides, the surface of the bone is eighteen occasionally irregular. When the reflection point of the wave from the transmitter 112 from that of the wave from the transmitter 110 to the recipient 114 As a result of these irregularities, the determination of the soft tissue velocity is incorrect. The wave from the transmitter 132 to the recipient 134 moves at an angle, so the irregularities have less influence on the reflection point.

8B shows another alternative measuring method using the transmitter / receiver, but there is a large time difference between the transmission and the reception, so that the reception quality is not deteriorated.

• (a) Messen der Signalausbreitungszeit von einem Sender 150 zu einem Sender/Empfänger 156;
• (b) Messen der Signalausbreitungszeit von einem Sender/Empfänger 152 zu einem Empfänger 164;
• (c) Messen der Signalausbreitungszeit von einem Sender 154 zum Sender/Empfänger 152;
• (d) Messen der Signalausbreitungszeit vom Sender/Empfänger 156 zum Empfänger 160; und
• (e) Messen der Signalausbreitungszeit zwischen dem Sender 150 und dem Empfänger 164.

In the configuration of 8B several measuring steps are carried out, which include:

• (a) Measure the signal propagation time from a transmitter 150 to a transmitter / receiver 156 ;
• (b) measuring the signal propagation time from a transmitter / receiver 152 to a receiver 164 ;
• (c) measuring the signal propagation time from a transmitter 154 to the transmitter / receiver 152 ;
• (d) measuring the signal propagation time from the transceiver 156 to the recipient 160 ; and
• (e) measuring the signal propagation time between the transmitter 150 and the receiver 164 ,

The speed of sound of the bone eighteen is determined in the manner described above. It should be appreciated that the measurement steps may be performed concurrently, but the transmitter / receiver preferably does not transmit waves just before they are to receive waves.

The Measuring the speed of sound of bones has many uses. A first application possibility is the finding of fractures and deformations in bones. When a Bones overloaded or is broken (also a hairline fracture on x-rays barely recognizable) changes its speed of sound noticeable in the places that the fracture surround. Because of the high resolution of some embodiments of the present invention fractures in the wrist bones are also identified, whereby prior art devices become such Distinction are not able.

A second application is the estimate of the bone and parts thereof, to the absence of minerals in the bone due to bone disease, osteoporosis and a To determine the environment with low gravity. It should be noted be that the speed mainly depends on the Young's modulus, d. H. the lower the speed, the weaker it is the bone.

A third application is the graphical representation of the healing process of a broken bone. The common practice is to hold the damaged bone in the plaster until a predetermined period of time has elapsed. However, some patients require a longer or shorter healing period. X-ray images usually do not show enough detail to evaluate the strength of the bone. By measuring and displaying changes in the speed of sound of the bone, a physician can more accurately assess the condition of a bone restoration. In a preferred embodiment, a small hole is drilled in the plaster and the speed of sound of the bone is measured without removing the plaster. In some patients, it is beneficial to change the Compare the speed of sound of the bone on opposite limbs.

A fourth application of the invention is to measure the thickness of the cortex of the bone. 9 shows a bone eighteen with an inner core 316 and a cortex 314 , The general diameter of the bone eighteen is D and the diameter of the inner core 316 is d. Thus, the thickness of the cortex 314 (D - d) / 2.

According to another embodiment of the present invention, a control unit estimates 100 the thickness of the cortex 314 using a theoretically derived and empirically confirmed dimensionless curve of the normalized velocity as a function of the normalized thickness 10 to which reference is now made. An explanation of the generation of the curve of 10 is stated in the book "Stress Waves in Solids" by H. Kolsky, Oxford and Clarendon Press, 1953.

The exact shape of the curve changes with the material being measured. It is, however, by the current Inventors have found that the shape of the curve for human Bone approximately is constant.

The velocity V _t in the curve of 10 is normalized by the velocity V ₀ that would be achieved in an infinite solid, and the thickness is normalized by the wavelength λ of the signal from the transmitter 70 , λ is of course determined by V ₁₈ : λ = V eighteen / f (41) where f is the frequency of the ultrasonic signal. It has been found by the inventors that the curve is about the same regardless of whether the thickness is about the thickness D (FIG. 9 ) of the bone or about the thickness (D - d) / 2 ( 9 ) of the cortex 314 is. The proposed explanation is that when the cortex is thick with respect to λ, the inner portions of the bone have no effect on the speed of sound. However, when the cortex is thin with respect to λ, the internal portions of the bone have an influence on the speed of sound. The inner sections of bones are usually much softer than the cortex, so that their speed of sound is much smaller than the speed of sound of the cortex. As a result, when a higher frequency is used, a thinner bone can be measured.

It is noted that the curve is an area 330 for relatively low speed ratios and small diameter / wavelength ratios and range 332 for diameter / wavelength ratios greater than about 1.5, which is an asymptote to 1.0.

To the thickness (D - d) / 2 for a bone eighteen estimate, becomes a sender 70 operated twice, once with a high-frequency input signal and once with a low-frequency input signal. At each measurement, the control unit 100 operated as above with reference to the 4A and 4B was described to measure the received speed. Alternatively, the transmitter 70 In a preferred embodiment of the present invention, a broadband transmitter is operated only once. In addition, the control unit contains 100 Frequency filter for separating the received high-frequency signals from the low-frequency signals. This simultaneously measures speed at high frequencies and speed at low frequencies.

The response to the high frequency input signal having a low wavelength λ gives a velocity data point 334 somewhere in the area 332 from which the velocity V ₀ can be determined. The exact location of the data point 334 is unknown because the thickness has not yet been determined. It is unimportant, however.

The response to the low frequency input signal results in a velocity data point 336 somewhere in the area 330 , Since the velocity V _{t is known} from the measurement and the velocity V ₀ from the previous measurement is known, the position of the data point is on the curve 336 known. Therefore, the ratio (D - d) / 2 · λ) can be determined. Since λ is out of the frequency of the transmitter 70 is known and the speeds are known, the thickness of the cortex 314 (D - d) can be determined.

It should be appreciated that the fourth use described above is more convenient if, instead of using prior art methods, the method of determining the speed of sound in the bone is used. High frequency signals are damped very quickly as they move through bone material. Therefore, only when the way in the bone eighteen short is how this is done Use of the present invention is possible, high-frequency ultrasonic waves appropriate. Thus, in a preferred embodiment of the invention, the high-frequency input signal used is higher than in the prior art, which makes it suitable for thinner bones.

It It should be recognized that the method described above for Emitting a single wideband signal instead of two signals with specific frequency in prior art methods for Determining the bone thickness can be applied, such as the Method described in US Patent 5,143,072 are shown.

There is now a reference to the 11 and 12 , which illustrate aspects of another embodiment of sampling over a section 448 of a human body, such as an arm, is useful.

In this embodiment, a sensor consisting of an array of ultrasonic transmitter / receiver cells 450 is formed on a section 448 is arranged or wrapped around this or he is as a stocking-like element 460 educated. The order 450 is typical with the section 448 acoustically coupled in the usual way.

As in 12 3, the input and output lines of each cell are the array 450 typically with an analog matrix multiplexer 451 connected, in turn, with a drive device 452 and with a signal processing unit 454 is coupled. The drive device 452 and the unit 454 are typically via a microprocessor 455 controlled.

The multiplexer 451 allows one access to each cell of the array 450 and is operated to define each cell as a receiver, a transmitter, a transceiver, or as inactive.

The individual cells of the arrangement 450 can be due to the attenuation caused by long distances through the bone eighteen is too small to form ultrasonic transducers in prior art methods. Because of this, multiple groups of cells become the arrangement 450 electronically and selectably defined as ultrasonic elements at desired locations. In a preferred embodiment of the present invention, each cell is the assembly 450 a separate ultrasonic element as described above. Alternatively, groups of cells are defined as transducers, as shown in the prior art. However, one of the modes described below is preferably used.

One The first preferred method of operation is cells and groups to select from cells that the functionality the embodiments described above approximately To run. As a result, an optimal placement of transceivers can be achieved be moved without ultrasonic elements.

• (a) Bestimmen der Dicke des darunter liegenden Weichgewebes 22; und
• (b) Konfigurieren der Anordnung 450 als Sender, Empfänger und Sender/Empfänger, zwischen denen sich optimale Abstände befinden, die anhand der bestimmten Dicke des Weichgewebes 22 berechnet werden.

In a preferred embodiment of the invention, a two-step process is used to control the configuration of the device 450 as sender and receiver. As described above, a preferred embodiment of the invention utilizes sensors that provide for a specific thickness of soft tissue between the sensor and the bones eighteen are optimized. Using the assembly 450 to image the bone eighteen It is possible to change the thickness of the underlying soft tissue 22 to determine before the bone velocity is determined:

• (a) Determine the thickness of the underlying soft tissue 22 ; and
• (b) Configure the arrangement 450 as transmitter, receiver and transmitter / receiver, between which there are optimal distances, based on the determined thickness of the soft tissue 22 be calculated.

An ultrasonic sensor alternatively comprises one or more transmitters and / or receivers as well as a cell arrangement. The cell assembly is configured to be used in place of some but not all of the ultrasonic elements described in the above embodiments. In the embodiment of 5A can z. B. the transmitter / receiver 82 and 84 be emulated by a cell array.

A second preferred method of operation is to form bones and soft tissues by operating different cells of the assembly 450 instead of the movement of a unit comprising several ultrasonic units. Thereby, the bone velocity can be measured at different positions and in different directions without physically moving the device.

It It should be noted that many methods of the prior art to determine the speed of sound of bones an inaccurate estimated value for the Use values of soft tissue thickness and soft tissue velocity. If an embodiment The present invention uses more accurate values for thickness and to determine soft tissue velocity, these methods provide the prior art more accurate results.

Besides that is the soft tissue velocity useful for the Determination of water, fat and muscle content of the tissue. Thereby Dehydration and rehydration of a patient can be analyzed by adjusting the soft tissue velocity in a selected part of the body of the patient over one Time period is measured. The muscle / fat ratio of the tissue can be determined when the water content of the tissue is known, or by Averaging multiple results that will be recorded before and after a patient drinks water.

If The human female breast is scanned, the air / tissue interface as a reflection plane can be used. The breast is preferably pressed against an elastic shape, so they are during the image does not move.

In a preferred embodiment According to the present invention, the scanning is performed using a Cell arrangement executed, as described above. The samples preferably comprise Samples of the same soft tissue from several directions, so that a velocity image of the tissue is preferably using can be reconstructed by tomographic methods.

The 13A and 13B show a preferred embodiment of the invention, which relates to the soft tissue imaging. 13A shows a general soft tissue section 508 that has a soft tissue section 506 contains, which has a significantly different speed of sound. An example of such tissues is a human breast and a pathologic tumor, such as a malignant tumor. The sensor preferably used comprises an arrangement, wherein a plurality of the cells 502 include a scanner known in the art of ultrasound imaging. At least one cell holds a transmitter 500 and at least one cell comprises a receiver 504 , The scanner 502 feels tissue 508 off until the place of the tissue 506 is found (wherein a scanning beam is indicated by two parallel lines). The tissue 506 otherwise it is not visible using normal ultrasound imaging. In this case, the position of the tissue 506 preferably prior to the use of another image forming method which also determines characterizing features. These distinguishing features are provided by the scanner 502 found and the position of the tissue 506 is determined. The soft tissue velocity of the tissue 508 in areas that the tissue 506 surrounded, is determined, the transmitter 500 , the recipient 504 and the multiple cells that make up the scanner 502 used, using the determination methods described above. Subsequently, the soft-tissue velocity is determined in a manner that determines the course of the measuring wave through the tissue 506 forces. If z. For example, when using a cell grid, multiple soft tissue measurements are taken and measurements that are significantly different are believed to pass through the tissue 506 have gone.

13B shows in conjunction with 13A a method of increasing the difference between the measurement of tissue velocity 508 and the measurement of tissue velocity 506 , The propagation time in the segments Aa, bB, Bd, Bb ', Dd' and a'A 'are constant and are due to the presence of the tissue 506 unaffected. These propagation times can be determined beforehand in areas containing the tissue 506 not included. Consequently, the tissue velocity in the tissue 506 can be better determined by using only the segments dd 'and b'a'. Alternatively or additionally, knowledge of the approximate depth of the tissue may be helpful 506 used to improve the difference in a similar way.

A soft tissue imaging device may include only two transceivers as described above with reference to methods for determining soft tissue velocity. However, such a device preferably comprises a plurality of ultrasonic elements and preferably an arrangement such as the arrangement 450 (in the 11 is shown). Alternatively, an apparatus as described above with reference to sound velocity determination in bones other than that used for soft tissue velocity determination may be used. In these cases, typically, the bone propagating wave is either not generated, not received, or analyzed.

A single measurement is merely in some preferred embodiment of the invention 2.5 ms, which is faster than most body rhythms. Several measurements, taken in the course of a body rhythm can, can used to measure the influence of body rhythm on the measurement to eat.

The Embodiments described above were related to a bone that is surrounded by soft tissue, described. However, one skilled in the art will recognize that these embodiments also useful are for the determination of the mechanical properties of a general Structure covered by a layered Material is surrounded, which has a lower speed of sound has. This concerns z. B. metal clips enclosed in rubber are.

As has been described above, the sound velocities in one two-layered structure determined. It should be recognized that the Sound velocities in a multi-layered structure under the Condition can be determined that the layers are in an increasing order of sound velocities are located. If z. B. a fast position with a slow position is covered and this further covered with a very slow position is, the sound velocity of the very slow position is first determined then the slow location and then the fast location certainly. Each determined speed is used for determining the speeds in the next Location used. However, if the slow location and the fast location are reversed, the slow position is covered by the fast location and the speed of sound of the slow position can not be determined become.

14 shows an embodiment of the invention used in conjunction with a scan-type ultrasonic sensor. A typical scanning ultrasonic sensor uses an array of cells, such as the arrangement described above 450 to form a scanning beam comprising a body portion, such as the bone eighteen and the overlying soft tissue 22 , scans. In a preferred embodiment of the present invention, the speed of sound of the bone eighteen simultaneously with the palpation of the bone eighteen certainly. This will create an image of the bone eighteen recorded together with a representation of the speed of sound of the bone or bone strength in the same area. Multiple cells 456 form a scanning transmitter and several cells 458 form a receiver for imaging the bone eighteen , The sound velocity of the bone is preferably determined between sampling pulses.

Claims (55)

Method for determining mechanical properties a solid, the one surface and a second velocity of sound, via an inserted medium, having a first sound velocity, the method includes: Transmitting a first ultrasonic wave along a transmission path from a first place through the inserted medium, along the surface and from the surface through the inserted Medium to a second location, wherein the inserted medium is a biological Contains tissue; measure up a first propagation time of the first wave along the transmission path; Determine the thickness of the inserted medium; Determining the first sound velocity; and To calculate the second sound velocity using the first propagation time, the distance between the places, the specific thickness of the inserted medium and the determined sound velocity in the inserted medium. The method of claim 1, comprising: Send a second ultrasonic wave from a third location through the inserted medium to the surface; measure up a second propagation time of a part of the second wave, the from the surface is reflected to a fourth location; Sending a third Ultrasonic wave from a fifth Place by the inserted Medium to the surface; and measure up a third propagation time of a part of the third ultrasonic wave, from the surface to the fifth Location is reflected. The method of claim 2, wherein the part of the second Wave and the part of the third wave essentially in the same place on the surface be reflected. A method according to claim 2 or claim 3, which comprises: Determining the first sound velocity using the distance between the third and the fourth location and the measured second and third propagation time of the second and the third ultrasonic wave. The method of claim 4, wherein the first sound velocity is determined using the following equation:

where V is the first sound velocity, D is the distance between the third and fourth locations, T ₁ + T _{2 is} the second propagation time of the second wave, and T _{3 is} the third propagation time of the third ultrasonic wave. Method according to one of claims 2-5, wherein the determination the thickness includes: Determining the thickness of the medium based on the Distance between the third and the fourth place and the measured second and third propagation time for the second and third, respectively Ultrasonic wave. Method according to one of claims 2-4, wherein the determination the thickness includes: Determine the thickness based on the specific first sound velocity and the third propagation time for the third Ultrasonic wave. The method of claim 2 or claim 7, wherein the thickness is determined using the following equation: H = V · T where V is the first sound velocity, T is the measured third propagation time of the third ultrasonic wave, and H is the thickness of the inserted medium. Method according to one of claims 2-8, wherein a path of the second Ultrasonic wave at least partially overlaps with the transmission path of the first ultrasonic wave. Method according to one of claims 2-9, wherein the thickness of a Intersection between the solid and the second ultrasonic wave is determined. Method according to one of the preceding claims, in the solid includes a biological tissue. The method of claim 11, wherein the solid has a in vivo living bone (in vivo bone). Method according to one of claims 1-12, wherein the thickness of a Intersection between the first ultrasonic wave and the solid determined becomes. Method according to one of the preceding claims, in the inserted one Medium comprises a living tissue. Method according to one of claims 2-14, wherein the first and the second ultrasonic wave are waves with a single frequency. Method according to one of claims 2-15, wherein the first, the second and the third place are in one plane, the Method includes: Tilting the plane relative to the surface edge over one Angle range; and Repeat the measurement of the first propagation time at different tilt angles. The method of claim 16, wherein the measurement accomplished when the distance between the first place and the surface is the same is a distance between the second location and the surface. A method according to claim 16 or claim 17, wherein the velocity of sound of the inserted Medium, which is below the first place or below the second place, is different. A method according to any of claims 16-18, which comprises determining a dependence the speed of sound in the solid body comprises the tilt angle. A method according to any one of claims 16-19, comprising determining a maximum determined sound velocity for the solid state. A method according to any one of claims 16-19, comprising determining a includes minimum specific sound velocity for the solid. Method according to one of claims 19-21, wherein the first, the second and third place are essentially colinear and at the tilting tilting the plane perpendicular to an axis that is colinear to the first, second and third locations. Method according to one of claims 2-22, wherein the first and the second propagation time are measured simultaneously. Method according to one of the preceding claims, in a frequency of at least the first ultrasonic wave at least 2 MHz. Method according to one of the preceding claims, in a frequency of at least the first ultrasonic wave at least 5 MHz. Method according to one of the preceding claims, in a frequency of at least the first ultrasonic wave at least 10 MHz. Method for determining mechanical properties of a solid over one inserted Medium having a first sound velocity, wherein the solid below the medium and a surface and a second sound velocity has, wherein the method comprises: Measuring the first sound velocity, being the inserted one Medium is a biological tissue; Measuring a propagation time the sound waves along a path, which by the inserted Medium and the solid runs; To calculate the second sound velocity using the first sound velocity and the propagation time through the inserted medium and the solid; and Determine the mechanical properties based on the second sound velocity. The method of claim 27, wherein the measurement the first sound velocity includes: Sending a first Sound wave from a first place through the inserted medium to the surface; measure up a first propagation time of a part of the first ultrasonic wave, from the surface is reflected to a second location; Sending a second one Ultrasonic wave from a third location through the inserted medium to the surface; measure up a second propagation time of a part of the second ultrasonic wave, from the surface is reflected to the third place; and Determine the first Speed of sound using the distance between the first and second place and the measured first and the measured second propagation time for the first and the second ultrasonic wave, respectively. Device for determining a second sound velocity of a solid ( eighteen ), which has a surface, via an inserted medium ( 22 ) having a first sound velocity, comprising: an ultrasonic transmitter ( 40 . 70 . 80 . 90 . 110 . 130 . 132 . 138 . 140 . 150 ), the first waves and second waves in the inserted medium ( 22 ) to the surface, the inserted medium ( 22 ) comprises a biological tissue; an ultrasonic transmitter / receiver ( 42 . 72 . 82 . 84 . 92 . 94 . 96 . 112 . 114 . 116 . 118 . 152 . 156 ), which receives the second waves after being reflected from the surface, and third waves into the inserted medium ( 22 ) is generated to the surface and receives it after being reflected from the surface; an ultrasonic receiver ( 44 . 74 . 86 . 98 . 120 . 134 . 136 . 142 . 144 . 156 . 164 ), which receives the first waves, wherein the first waves through the inserted medium ( 22 ) to the surface, along the surface and from the surface to the inserted medium ( 22 ) and have spread to the ultrasound receiver; and a control unit ( 100 ), which controls the ultrasonic transmitter and the transceiver to generate the first, second and third waves, receives signals in response to ultrasonic waves received from the transceiver and the receiver, and has the shortest propagation time for each of first, second and third waves and determines the distance between the transmitter and the receiver, the distance between the transmitter and the transmitter / receiver and the propagation time used to determine the thickness of the inserted medium and the first speed and the second speed of sound in Reaction to the specific thickness and the specific first speed to calculate. Apparatus for determining a second sound velocity of a surface possessing solid ( eighteen ) via an inserted medium ( 22 ) having a first sound velocity, comprising: an ultrasonic transmitter ( 40 . 70 . 80 . 90 . 110 . 130 . 132 . 138 . 140 . 150 ), which injects a first wave into an inserted medium ( 22 ) to the surface, the inserted medium ( 22 ) comprises a biological tissue; an ultrasonic receiver ( 44 . 74 . 86 . 98 . 120 . 134 . 136 . 142 . 144 . 156 . 164 ), which receives the wave, whereby the first wave through the inserted medium ( 22 ) to the surface, along the surface and from the surface to the inserted medium ( 22 ) and has moved to the ultrasound receiver; an ultrasound unit ( 42 . 72 . 82 . 84 ) receiving a second wave from the transmitter or transmitting it to the receiver, the second wave being reflected at a non-right angle to the surface and generating third waves, the ultrasonic unit detecting the third waves reflected from the surface , receives; and a control unit ( 100 ) which controls the ultrasonic transmitter to generate the first wave, controls the ultrasonic unit to generate the third wave and to transmit the second wave to the receiver, the controller responsive to the waves coming from the receiver and from the receiver Ultrasonic unit are received, receiving signals and determines the shortest propagation times of each of the first, second and reflected waves and the distance between the transmitter and the receiver, the distance between the ultrasonic unit and the transmitter or receiver and the propagation times used to the thickness of the inserted medium and determine the first speed and calculate the second speed of sound based on the determined thickness and the determined first speed. Device according to Claim 30, in which the ultrasound unit ( 42 . 72 . 82 . 84 ) at least one ultrasonic transmitter / receiver ( 42 . 72 . 82 . 84 . 92 . 94 . 96 . 112 . 114 . 116 . 118 . 152 . 156 ). Device according to Claim 30, in which the ultrasound unit ( 42 . 72 . 82 . 84 ) at least two ultrasonic transceivers ( 42 . 72 . 82 . 84 . 92 . 94 . 96 . 112 . 114 . 116 . 118 . 152 . 156 ). Device according to Claim 30, in which the ultrasound unit ( 42 . 72 . 82 . 84 ) at least three ultrasonic transceivers ( 42 . 72 . 82 . 84 . 92 . 94 . 96 . 112 . 114 . 116 . 118 . 152 . 156 ). Device according to Claim 30, in which the ultrasound unit ( 42 . 72 . 82 . 84 ) at least four ultrasonic transceivers ( 42 . 72 . 82 . 84 . 92 . 94 . 96 . 112 . 114 . 116 . 118 . 152 . 156 ). Device according to one of claims 29 or 31-34, in which the at least one transmitter / receiver comprises a transmitter ( 40 . 70 . 80 . 90 . 110 . 130 . 132 . 138 . 140 . 150 ) and a receiver ( 44 . 74 . 86 . 98 . 120 . 134 . 136 . 142 . 144 . 156 . 164 ). Device according to one of Claims 30-34, in which the ultrasound unit is located approximately in the middle between the ultrasound receiver ( 44 . 74 . 86 . 98 . 120 . 134 . 136 . 142 . 144 . 156 . 164 ) and the ultrasonic transmitter ( 40 . 70 . 80 . 90 . 110 . 130 . 132 . 138 . 140 . 150 ) is arranged. Device according to one of claims 30-35, wherein the ultrasound unit is substantially closer to either the ultrasound receiver ( 44 . 74 . 86 . 98 . 120 . 134 . 136 . 142 . 144 . 156 . 164 ) or at the ultrasonic transmitter ( 40 . 70 . 80 . 90 . 110 . 130 . 132 . 138 . 140 . 150 ) is arranged as in the other of the ultrasonic receiver or the ultrasonic transmitter. Device according to one of claims 30-37, wherein the ultrasonic receiver ( 44 . 74 . 86 . 98 . 120 . 134 . 136 . 142 . 144 . 156 . 164 ), the ultrasonic transmitter ( 40 . 70 . 80 . 90 . 110 . 130 . 132 . 138 . 140 . 150 ) and the ultrasound unit are not colinear. Device according to one of claims 30-37, wherein the ultrasonic receiver ( 44 . 74 . 86 . 98 . 120 . 134 . 136 . 142 . 144 . 156 . 164 ), the ultrasonic transmitter ( 40 . 70 . 80 . 90 . 110 . 130 . 132 . 138 . 140 . 150 ) and the Ultrasonic unit ( 42 . 72 . 82 . 84 ) are substantially colinear. Device according to one of claims 30-39, wherein the ultrasonic receiver ( 44 . 74 . 86 . 98 . 120 . 134 . 136 . 142 . 144 . 156 . 164 ) and / or the ultrasonic transmitter ( 40 . 70 . 80 . 90 . 110 . 130 . 132 . 138 . 140 . 150 ) and / or the ultrasound unit ( 42 . 72 . 82 . 84 ) are oriented to the surface at an angle. Device according to one of claims 28-40, wherein a portion of the device with the inserted medium ( 22 ) is substantially in contact and extends over a length that is less than or equal to 100 millimeters. Apparatus according to claim 41, wherein the length is smaller or equal to 50 millimeters. Apparatus according to claim 43, wherein the length is smaller or equal to 3 millimeters. Method according to one of claims 1-28, wherein the solid ( eighteen ) comprises a tooth. A method according to any one of claims 1-28 or claim 44, wherein the solid state a curved one Bone includes. A method according to any one of claims 1-28 or claims 44-45 the solid one Whirl includes. Process according to any one of claims 1-28 or claims 44-46, wherein the solid ( eighteen ) comprises a portion of a bone that is substantially proximate to a joint. A method according to any one of claims 1-28 or claims 44-47 the solid one Includes wrist bone. The method of any of claims 1-28 or claims 44-48, further comprising: Determine a later one Speed of sound, after the second speed of sound has been determined, in the same place of the solid; and to compare the second speed with the later speed of sound, about changes in a structure of the solid to determine. A method according to any one of claims 1-28 or claims 44-49 the measurement in a given direction on the body tissue accomplished and further comprising: Determining a vertical sound velocity in the same place of the solid in a second direction, the vertical speed of sound is substantially perpendicular to the given direction. Device according to one of claims 30-37, wherein the non-vertical reflected wave is sent from the ultrasound unit. Device according to one of Claims 30-37, in which the non-perpendicular reflected wave is transmitted through the transmitter ( 40 . 70 . 80 . 90 . 110 . 130 . 132 . 138 . 140 . 150 ) is sent. Device according to Claim 29, in which the ultrasound receiver ( 44 . 74 . 86 . 98 . 120 . 134 . 136 . 142 . 144 . 156 . 164 ), the ultrasonic transmitter ( 40 . 70 . 80 . 90 . 110 . 130 . 132 . 138 . 140 . 150 ) and the transmitter / receiver ( 42 . 72 . 82 . 84 . 92 . 94 . 96 . 112 . 114 . 116 . 118 . 152 . 156 ) are not colinear. Device according to Claim 29, in which the ultrasound receiver ( 44 . 74 . 86 . 98 . 120 . 134 . 136 . 142 . 144 . 156 . 164 ), the ultrasonic transmitter ( 40 . 70 . 80 . 90 . 110 . 130 . 132 . 138 . 140 . 150 ) and the transmitter / receiver ( 42 . 72 . 82 . 84 . 92 . 94 . 96 . 112 . 114 . 116 . 118 . 152 . 156 ) are substantially colinear. Device according to Claim 29, in which the ultrasound receiver ( 44 . 74 . 86 . 98 . 120 . 134 . 136 . 142 . 144 . 156 . 164 ) and / or the ultrasonic transmitter ( 40 . 70 . 80 . 90 . 110 . 130 . 132 . 138 . 140 . 150 ) and / or the ultrasonic transmitter / receiver ( 42 . 72 . 82 . 84 . 92 . 94 . 96 . 112 . 114 . 116 . 118 . 152 . 156 ) are oriented to the surface at an angle.